Arc lamp



C. S. ASHCRAFT ARC LAMP Sept. 18, 1928. 1,684,655

Filed Sept. 19, 1923 5 Sheets-Sheet 1 (answer e1 imam/V Sept 18, 1928.

C. S. ASHCRAFT ARC LAMP Fi1ed Sept. 19,- 1925 3 Sheets-Sheet 2 CAME/v05JAmcm/ r Patented Sept; 18, 1928.

' UNITED STATES CLARENCE S. ASHCRAFT, F LOS ANGELES, CALIFORNIA.

ABC LAMP.

Application filed September 19, 1923. Serial No. 663,569.

This invention relates to are lamps of the type provided withelectrically operated mechanisms for feeding, the electrodes towards theare so as to compensate for the disintegration of the electrodes at thearc and thereby maintain a substantially constant are during operationof the lamp. This invention is a continuation in part of my co-pendingapplication, Serial No. 488,849, filed August 1,1921.

In my co-pending application there is described an arc lamp havingelectrically operated mechanisms for automatically maintaining aconstant are between the electrodes.

However with the lamp of the co-pending application the electrodes mustbe manually adjusted by an operator when lamp is to be started so thatthe electrodes may be struck togeth-- er and the are formed. Thiscompelled the lamp to be positioned where it was within reach of theoperator and had a further disadvantage that the striking together ofthe electrodes burnt away one side of the crater on the positiveelectrode with the result that a dark spot could be seen in the radiatedlight which persisted several minutes after the are lamp was started.

An important object of this invention is to provide a form of arc lampwhich is entirely automatic in operation and automatically and rapidlyestablishes the are when current is supplied to the lamp andautomatically adjusts the length of the'arc to maintain a constant arcwhile the lamp is in operation, so that resultant lamp may be operatedfrom a locality or position spaced from the lamp.

By this invention notonly is the necessity of manually striking thearceliminated but the arc is rapidly established with the result 4 that thecrater of the positive is not destroyed and the lamp starts immediatelyto send off a uniform ray of light. i e

Another 'ob eet of this invention is to pro vide a niore'simple{and"economi'c'abmechanisi'nfo'r maintaining a uniform length of arethan tlie mechanism described" in said 00 pending application.Morespeci'ficallyone objectjof this invention is to providea more isi'mple ineans forinterrupting the feeding of the positive "electrode't'vhen an interrupted feed is required and another object is toprotitle a mam-arse Qmaking' ?the negative feed y contin u o'us"andalways in the tlii'ection" of the are. 55 Another object of thisinvention is to provide an arc lamp in which the relation between thespeeds at which-the positive electrode and the negative electrodeadvance may be varied and controlled at will in the are scription of theaccompanaying drawings and will be found in practice or use of the,

invention. In the accompanying drawings I have illustrated a preferredexample embodying this invention, but desire to be understoodto theefi'ect that while such preferred example incorporates the spirit ofthis invention, various changes may be made in the form of the lampwithout departing from the spirit of the invention.

In the drawings Figure 1 is a side elevation of this embodiment of theinvention.

Fig. 2 is a rear elevation of mechanism for interrupting feed of thepositive electrode. 4

/ Fig. 3 is a side view of the mechanism shown in Figure 2.

Fig. 4 is a view looking in a direction par-- allel to the axis of thenegative electrode of the negative operating mechanism.

Fig. 5 is a section on the line 5 5 of Fig.

through the so Fig. 9'is-a section on the liner9.9a,ofFig.z8p Inthedrawings, the are lamp-is provided with a: positive electrode.generally indicated by-A and a negative electrode genera'llyindie catedby Bfi The' electrodes' are arranged with one end of each? electrodeadjacent one end of the other elect-rode'and' theangle@be1-1 twee'nitheelectrodes is Z preferably. greater than 5 a right. angle and less; than135? 1 The; positive electrode; is. preferably -'positioned with itsaxis parallelftoithe directioihthe light is intended to be radiated. Inorder to produce a uniform intensity of are it is necessary to rotatethe positive electrode, otherwise the crater of the positive electrodewould become irregular in shape, elongated at one side more than theother. Under such conditions, the direction at which the light wasradiated would continually change.

It is likewise necessary to advance the electrodes of the lamp tocompensate for the rate at which the electrodes burn or disintegrate.

A mechanism for producing both a continu-- ous rotation of the positiveelectrode A and for advancing such electrode will now be described. Thepositive electrode A passes loosely thru a bushing 2 which encloses apor tion of the electrode. The bushing 2 is journa-lled by ananti-friction bearing 3 supported in a casting 4. Thebushing 2 providesa circular plate 5 surrounding the electrode A, which plate 5 isprovided with inwardly projecting brackets 6, each pair of bracketssupporting a stud 7 which engages in radial slots 8 formed in thebrackets, said slots permitting of radial movement of the studs relativeto the axis of the drum. Adjacent ends of studs 7 are connected to eachother by coiled springs 9, which yieldingly hold the studs 7 towards theaxis of the drum. The opposite ends of the studs 7 are provided withclamps 10 held together by a screw 11. On each stud 7 between each pairof brackets 6 is rotatably mounted aspur gear 12. In the drawings two ofsuch gears are illustrated, but it is understood that more or fewer ofsuch gears may be employed if desired. The gears 12 engage a spiral hoopgear 13 which is formed on the forward vertical face of a control member14 which is rotatably mounted on the bushing 2. The control member 14provides a means for controlling the rotation of the gears 12 abouttheir axes. Thus, if the control member 14 and the plate 5 mounting thegears 12 are both rotated at equal speeds the gears 12 Will not rotatearound their axis. If the rates of rotation of the control member 14 andthe plate 5 are not equal then the spiral hoop gear 13 will cause thegears 12 to rotate. Thegears 12 are adjusted by the screw 11 and tenslonof the spring 9, so that they engage the electrode A. Thus the rotationof the gears 12 will cause the electrode A to move in an axialdirection. The spiral hoop gear 13 1s formedso that when the rate ofrotation of the control member 14 is less than the rate of rotation ofthe plate 5 or bushing 2, the gears 12 are rotated in a direction tocause the electrode A to advance the electrode towards the arc. Therotation of the bushing 2 and plate 5 is effected through a bevelledgear 15 secured to the rear end of the bushing 2 and driven from a shaft16, carrying a bevelled gear 17 meshing with the gear 15.

The rotation of the control member 14 is regulated by a ear 18 formed onthe rear of said member. he gear 18 engages a pinion 19 secured to ahorizontal shaft 20 journalled in the casting 4. The shaft 20 isprovided with a ratchet wheel 21 engaged by a pawl 22. The pawl is rigidwith an arm 23 supporting a detent 24. The detent 24 is positioned withone end extending towards the back of the bevelled gear 15 where it mayengage one of a number of studs 25 projecting from the rear of said gear15. (See Fig. 2.). The detent 24 has screw engagement with the arm 23 sothat the detent may be screwed towards or away from the studs 25 as theoperation of the lamp may require. The pawl 22 and arm 23 as a unit arefixed to a shaft 26 which is journalled in the casting 4. 27 indicates aspring which yieldingly maintains the pawl 22 engaging the ratchet wheel21. By this construction the control member 14 is normally held fromrotating with the bushing 2 due to the pawl 22, engaging said wheel 21,and thus the electrode A is normally continually advancing towards thearc. Under certain conditions hereinafter described it is necessary tointerrupt-the feed of the electrode in which case the detent 24 is movedtowards the studs 25 until the studs 25 on rotating will engage thedetent and pivot the detent 24 back, against the pressure of the spring27, to permit the studs to pass. This releases the pawl 22 from thewheel 21 and the control member rotates with the rotation ,of thebushing 2, and the advance of the positive electrode 15 interrupted. Inthe drawings there is shown three of the studs 25 which will cause thefeed of the electrode A to be interrupted three times during eachrevolution of the bushing 2. Obviously more or less of the studs 25could be provided if desired. The length of time each stud willinterrupt the feed of the electrode A will depend upon the distance thedetent 24 is screwed towards the studs. To support the positiveelectrode A and its rotating and feed mechanism the casting 4 is securedto a horizontal support 28. Said support 28 is fixed to the top of aframe 29 by bolts 30 and electrically insulated from said frame by aninsulating block 31 between the frame 29 and support 28. The frame 29 isbolted at its lower end to a lower frame 32 which serves to supportcertain parts of the negative feeding mechanism.

The rear end 33 of the frame 32 is turned vertically downward. Bolts 34extending rearwardly from the frames 29 and 32 support verticalstandards 35 to which an electric motor 36 is fastened. The motor 36 isprovided with a worm 37 at the lower end of its armature shaft. A wormwheel 38 engages teeth of said worm and isfixed to a shaft 39 journaledin a housing 39' enclosing said worm and gear. The shaft 39 is providedwith a flexible coupling 40 and terminates in a worm shaft section 41.The shaft 16, -which drives the bushing 2, extends vertically downwardin the lamp and provides a worm Wheel 42 engaging the worm section 41.

From the foregoing it will be clear that operation of the motor 36willproduce a comparatively slow rotation of the electrode A, and. alsowhen the pawl 22 is engaging the wheel 21, will produce a rotation ofthe gears 12. The various gears are so proportioned relative to thespeed of operation of the motor 36 that the speed at which the electrodeA advances is just slightly faster than the speed at which the electrodeA is consumed, so that it is then possible with a minimum interruptionof the positive electrode to bring the speed of advance of the positiveelectrode equal to the speed at which said electrode is consumed. Exactadjustment of the detent 24 is not necessary since a further control ofthe speed at which the electrode advances is accomplished by automaticcontrol of the speed of the motor 36 in a manner hereinafter described.j

The mechanism for feeding the negative electrode 13 will now bedescribed. The vertical shaft 16 is provided at its medial portion witha bevelled gear 43 meshing with a bevelled gear 44 carried on a negativeelectrode operating horizontal shaft 45. The shaft 45 is j ournalled inthe frame 29. 46 indicates a frame pivotally mounted on the lower frame32. Said frame 46 provides a bearing 47 for a shaft 48 which is inclinedupward and joined by a universal joint 49 to the negative electrodeoperating shaft 45. The negative electrode is held by a clamp 50extending from a carriage 51. The carriage 51 is adapted to slide alongtwo parallel rods 52 secured together by blocks 53 at their ends, thecarriage 51 having tubular slides 54 telescoped over the rods.Journalled at its ends in the blocks 53 is provided a worm shaft55having a bevelled gear 56 meshing with a bevelled gear 57 fixed .tothe inclined shaft 48. The upper block 53 is bolted to a flange 58extending from the bearing 47 thus supporting the negative electrode Bon the pivoted frame 46. The carriage 51 is provided with a toothedcatch 59 which normally engages the worm shaft 51 to feed the carriage55 and electrode B upon rotation of the shaft 55.

The catch 59 is preferably fixed to a bar,

such as 60, which is pivoted to the carriage at one end and the otherend is yieldingly urged towards the worm shaft 55 by a spring 61, sothat while normally the catch is in engagement with the shaft 55 thecatch may be released to manually shift the electrode along the rods 52.

Below the frame 32 is secured a solenoid 62 which provides an automaticmeans for striking the are when operation of the lamp is to be started.The solenoid comprises an electro-Inagnet 63 having an armature 64, Thearmature 64 is fixed to an arm 65 provided by the pivoted frame 46 andis pressed against a pin 66 engaging a coiled spring 67 set in the frontend of the solenoid. 68 indicates a bolt which may be adjusted to varythe pressure exerted by the spring 67 through the pin 66 upon thearmature 64.

The electro-magnet 63 is connected to the mains so that the current sentthrough the electro-magnet 63 will draw the armature 64 which will tendto cause the frame 46 to pivot upward and strike the positive electrodeA.

Referring to Fig. 7 the electrical wiring of the lamp. is shown. Thenegative supply main 70 connects with a ballast resistance 71 from whichcurrent is supplied to the negative electrode B being connected to theclamp 50 pressed across the elcctro-magnet 63 and motor 36.

\Vhen the arc lamp is to be operated the current is first switched on.At the time the current is turned on 'the current cannot flow across thegap between the electrodes and start the arc unless the electrodes arefirst struck together. This striking of the electrodes is effected bythe solenoid. The electro-magnet 63 of the solenoid is constructed sothat when the lamp is in operation the current through the magnet 63 isinsufficient to draw the armature 64 into the magnet and pivot theelectrode B up to strike the electrode A. Before the arc is struck,however, a much larger current is sent through the electro-magnet 63 dueto the high resistance of the gap between the electrodes, and under suchconditions the electrode is rapidly forced upward to strike the arc.When the electrodes strike together the resistance to travel of thecurrentthrough the electrode path becomes practically zero andaccordingly the current through the electromagnet 63 becomes very lowpermitting the electrode B to immediately drop back from electrode A.

The motor 36 then rotates at av speed pro portional to the voltageacross the arc and advances both electrodes at a rate to compensate forthe disintegration of the electrodes. Thus if the speed of theelectrodes becomes insuiiicient to equal the rate of con sumption of theelectrodes the resistance across the arc will increase, producing ahigher are voltage, this causes a greater current to be sent through themotor and accordingly the same will speed up, and likewise when thespeed at which the electrodes advance becomes too rapid the length ofthe arc will decrease, resulting in a decrease in lift the resistanceacross the arc lowering the arc voltage and less current will then flowthrough the motor and the speed of advance of the electrodes will beretarded.

However, in cases where a great variation in the voltage on the mainsmay occur the motor 36 may not be able to maintain the are constant withbot-h the feeds of the negative and positive electrodes continuous. Insuch cases it is preferable to fix the pitch of the hoop gear 13 so thatthe positive electrode will normally feed slightly faster than theelectrode is consumed and adjust the feed of the positive electrode withthe interrupting mechanism. However. it is to be remembered thatcontinuous feed of the positive electrode produces the most uniform arc,and that when the feed must be interrupted at short intervals, the timeduring which the feed is interrupted should preferably be less than thetime during which the electrode is feeding toward the are.

I have found that this manner of feeding the positive electrode enablesthe arc lamp to burn as long as five to ten times the period of timethat an arc lamp, in which the positive electrode is jerked towards thearc and the periods of interruption greatly er;- ceed the periods duringwhich the positive electrode is being fed, can be burned withoutrequiring attention from the operator.

Other advantages of this invention are that V the lamp is entirelydependable in operation,

electrodes of varying diameters may be employed, the lamp is easy tooperate, simple and economical in construction.

I claim:

1. In an arc lamp having a positive electrode, a negative electrode, andmeans for advancing the electrodes, the combination of: an are strikingmeans comprising a negative electrode carriage so disposed as tonormally hold said negative electrode separated from saidpositiveelectrode by the weight of said carriage; and electro-magnetic meansoperative by the throwing on of the are circuit for striking saidnegative electrode against said positive electrode, the striking of theare being efi'ective to reduce the strength of the pull of saidelectro-magnet whereby the weight of the carriage will cause it to fallback to normal operating position.

2. In an arc lamp having a positive electrode, a. negative electrode,and means for advancing the electrodes, the combination of: an arestriking means omprising a negative electrode carriage so disposed as tonormally hold said negative-electrode separated from said positiveelectrode by the weight of said carriage; electro-magnetic meansoperative by the throwing on of the are circuit for striking saidnegative electrode against said positive electrode; and a compressionspring adapted to assist in return of the carriage to normal operatingposition.

3. In an arc lamp: an electrode holder; an electrode supported by saidholder; means for rotating said holder on the longitudinal axis of saidelectrode; means carried by said holder adapted to revolve therewith andto be rotated for advancing said electrode; a spiral gear mounted on andadapted to rotate with said holder and adapted to rotate said last namedmeans when its own rotation is retarded; and means for periodicallyretarding the rotation of said gear.

at. In an arc lamp; an electrode holder; an electrode supported by saidholder; means for rotating said holder on the longitudinal axis of saidelectrode; means carried by said holder adapted to revolve therewith andto be rotat d for advancing said electrode; a spiral gear mounted on andadapted to rotate with said holder and adapted to rotate said la t namedmeans when its own rotation is retarded; and means for periodicallyretarding the rotation of said gear, the last mentioned means comprisinga first gear secured to said spiral gear, a second gear adapted toactuate said first gear, and a pawl adapted to engage said second gearand to be moved out of engagement therewith by the rotational movementof said holder.

In an arc lamp': an electrode holder; an electrode supported by saidholder; means for rotating said holder on the longitudinal axis of saidelectrode; means carried by said holder adapted to revolve therewith andto be rotated for advancing said electrode; a spiral gear mounted on andadapted to rotate with said holder and adapted to rotate said last namedmeans when its own rotation is retarded; and means for periodicallyretarding the rotation of Said gear, the last mentioned means comprisinga first gear secured to said spiral gear, a second gear adapted toactuate said first gear, a pivoted pawl adapted to engage said secondgear and to be disengaged therefrom, a stud carried by said holder, adetent secured to said pawl and adapted to be moved by said stud,whereby said pawl is moved out of engagement with said second gear.

4. 6. A combination as described in claim 5 in which said detent isadjustable.

7. In an arc lamp: an electrode holder; an electrode supported by saidholder; means for rotating said holder on the longitudinal axis of saidelectrode; means carried by said holder adapted to revolve there withand to be rotated for advancing said electrode; a spiral gear mounted onand adapted to rotate with said holder and adapted to rotate said lastnamed means when its own rotation is retarded; means for periodicallyretarding the rotation of said gear, the last mentioned means comprisinga first gear secured to said spiral gear, a second gear adapted toactuate said first gear, a pivoted pawl adapted to engage said secondgear and to be disengaged therefrom, a stud carried -by said holder, adetent secured to said pawl and adapted to be moved by said stud,Whereby said pawl is moved out of engagement With said second gear; andmeans for returning said pawl into engagement with said second gear.

8. In an arc lamp: an electrode holder; an electrodecarried by saidholder; means for advancing said electrode in said holder; and meansactuated by said holder for periodically interrupting the action of saidmeans for advancing the electrode, said last named means including meansfor varying the period of duration of said interruptions.

9. In an arc lamp: an electrode holder;

means for rotating said holder; means actuated by the rotation of saidholder to advance an electrode disposed therein; and meansactuated bysaid holderperiodically relative to the rotation thereof to interruptsaid electrode advancing means.

10. In an arc lamp: an electrode holder; means for rotating said holder;means actuated by the rotation of said holder to advance an electrodedisposed therein; and means actuated by said holder periodicallyrelative to the rotation thereofto interrupt said electrode advancingmeans, the periodicity of the actuation of said last mentioned meansbeing adj ustahle.

Signed at Los Angeles, Californiaithis 31st day of July, 1928.

CLARENCE S. ASHCRAFT.

